Biological Physics · Cross-listed from cond-mat.soft
Non-Monotonic Exciton Transport Efficiency in Multi-layer Ring-shaped Quantum Networks inspired by Photosystem I
Yi Li, Rui Li, Kai-Ya Zhang et al. (+3 more)
Photosystem I (PSI) is one of the most efficient natural photosynthetic complexes and serves as a structural prototype for understanding excitation energy transfer (EET) and designing artificial light-harvesting systems. Here, we construct a multilayer elliptical-conical
quantum network inspired by PSI to investigate how
antenna architecture affects EET. Excitation dynamics are simulated using the
quantum jump approach combined with coherent modified Redfield theory (QJA-CMRT). The transfer efficiency exhibits a pronounced nonmonotonic dependence on pigment density, reaching a maximum of 0.86 at x=6 in the five-layer network. The optimal configuration contains 91 pigments, close to the number of core
antenna pigments in natural PSI. Our combined density-of-states and kinetic analyses reveal that this nonmonotonic dependence originates from a trade-off: at low pigment densities, enhanced band overlap promotes energy transfer, whereas at high densities, excessive
exciton delocalization compromises funnel directionality and reduces efficiency; the optimal configuration is consequently achieved at x=6. These findings provide insights into PSI
antenna organization and offer guidelines for designing efficient artificial light-harvesting systems.
Read the full abstract ▾
All authors Yi Li, Rui Li, Kai-Ya Zhang, Ming-Zi Jin, Tao Liu, Qing Ai
Applied Physics · Cross-listed from cs.ET
Programming Spintronic Reservoir Computing
Yuichiro Terasaki, Yusuke Imai, Jason Z. Kim et al. (+1 more)
We present a programming framework for a spintronic reservoir computer (RC) that maps prescribed input-output relationships directly onto the readout layer, bypassing conventional data-driven black-box approaches. Our spintronic RC is based on magnetoresistive random-access
memory and exploits magnetization dynamics for computation. We introduce a general metric that quantifies the system's programmability and reveals how the governing equations and system parameters constrain the class of realizable functions. We then construct externally controllable readout layers by exploiting the explicit parameter dependence of the prescribed equations. This metric and construction enable programming explicit functions on the spintronic RC, indicating a potential route to in-
memory computing. Our demonstrations include neural-network emulation, bifurcation
embedding, and a Newton solver for fifth-order algebraic equations. In addition, we prove the universal approximation property of the spintronic RC in the limit of infinite system size and input duration, and show its consistency with programmability.
Read the full abstract ▾
All authors Yuichiro Terasaki, Yusuke Imai, Jason Z. Kim, Kohei Nakajima
General Physics
Groups of Worldview Transformations Implied by Einstein's Special Principle of Relativity over Arbitrary Ordered Fields
Judit Madarász, Mike Stannett and Gergely Székely
In 1978, Yu. F. Borisov presented an axiom system using a few basic assumptions and four explicit axioms, the fourth being a formulation of the relativity principle; and he demonstrated that this axiom system had (up to choice of units) only two models: a relativistic one in which worldview transformations are Poincaré transformations and a classical one in which they are Galilean. In this paper, we reformulate Borisov's original four axioms within an intuitively simple, but strictly formal, first-order logic framework, and convert his basic background assumptions into explicit axioms. Instead of assuming that the structure of physical quantities is the field of real numbers, we assume only that they form an ordered field. This allows us to investigate how Borisov's
theorem depends on the structure of quantities. We demonstrate (as our main contribution) how to construct Euclidean, Galilean, and Poincaré models of Borisov's axiom system over every non-Archimedean field. We also demonstrate the existence of an infinite descending chain of models and transformation groups in each of these three cases, something that is not possible over Archimedean fields. As an application, we note that there is a model of Borisov's axioms that satisfies the relativity principle, and in which the worldview transformations are Euclidean isometries. Over the field of reals it is easy to eliminate this model using natural axioms concerning time's arrow and the absence of instantaneous motion. In the case of non-Archimedean fields, however, the Euclidean isometries appear intrinsically as worldview transformations in models of Borisov's axioms and neither the assumption of time's arrow, nor the rejection of instantaneous motion, can eliminate them.
Read the full abstract ▾
General Physics
Towards a Quantum Erlangen Program
Matthew J. Lake
The classical Erlangen Program sought to classify metric spaces entirely in terms of their
symmetries. In physical spacetimes, these
symmetries define transformations between classical reference frames, yielding a one-to-one correspondence between frame transformations and the underlying geometry. More recently, the classical notion of ideal frame has been extended to the
quantum regime, by considering observers as
embodied physical systems, subject to the laws of
quantum mechanics. Here, we build on this approach, but outline an alternative definition of the term `
quantum reference frame', which differs somewhat from the mainstream view. We then show how the new definition can be used to construct a simple model of Planck-scale spacetime, which makes contact with existing
quantum gravity phenomenology. Finally, we show how classical spacetime
symmetries can be “mathematically preserved but operationally broken”, in the new model, suggesting that
quantum spacetime may be classified, at least locally, in terms of transformations between quantised frames of reference.
Read the full abstract ▾
Chemical Physics
Channel selection at identically vanishing dissipation difference: isolating the frenetic sector of the overdamped path measure
Shlomo Segal
Transition-state and Kramers-Langer theory determine reaction channel selection from data at a single point: the saddle. We show this is insufficient in a precise, constructive sense. Using the standard split of the Onsager-Machlup path weight into a time-antisymmetric part fixed by the
entropy flux and a time-symmetric part, the frenesy, we first settle when a dissipation-based criterion can distinguish two forward histories at all: the
entropy difference between two histories sharing endpoints equals beta times the circulation of the non-conservative force around the loop they enclose, and vanishes identically for every gradient flow. We then construct a two-channel gradient landscape whose channels share both endpoints, whose barrier heights are equal identically, and whose saddle Hessians are the same
matrix. The
entropy sector is switched off by construction, all local saddle-point theories predict 50:50 exactly, and the branching ratio isolates the frenetic sector. Langevin simulation gives P(+) = 0.4568 +/- 0.0012. We identify a covariant
geometric contribution to pathway selection within the frenetic sector, (1/2) ln det(D_perp H_perp), show that the divergence-of-drift observable proposed for this role is not coordinate-invariant whereas this one is, and find that it reproduces the measured branching to within 0.5 sigma with no fitted parameters. Stiff spectator modes cancel identically, since selection depends only on a ratio of determinants. We also give a parameter-free prediction: a solenoidal force of strength epsilon must contribute exactly 2*beta*epsilon/pi to ln[P(+)/P(-)]. These results are an exactly controlled counterexample to the sufficiency of local saddle-point data for channel selection.
Read the full abstract ▾
Geophysics
High solubility of water in post-perovskite and bridgmanite in the Earth's deep lower mantle
Megumi Semba, Naoya Sakamoto, Shuhei Mita et al. (+5 more)
Water in the Earth's mantle induces melting, giving rise to strong chemical heterogeneity, and alters its rheological and transport properties, which are keys to understanding seismic-wave speeds anomalies, convective motions and electrical conductivity. However, the abundance of water and its role in the deep mantle remain uncertain and controversial, particularly at conditions of the core-mantle boundary (CMB) region. Here we carry out melting experiments on a hydrous, natural mantle composition including both $H_2O$ and $D_2O$ over the entire pressure range of the Earth's lower mantle, in which melt coexists with bridgmanite (Bdg) and/or post-perovskite (PPv), the primary constituents of the respective lower and lowermost mantle. High-resolution secondary-ion mass spectroscopy (Cryo-SIMS) measurements reveal high water concentrations in Bdg (up to 5,500 ppm by weight) and PPv (up to 1.22 wt%) with strong enrichment in deuterium/hydrogen (D/H) relative to coexisting melt. The high solubilities of water in Bdg and PPv at CMB conditions suggest that subducting slabs do not release water when they reach the bottom of the mantle, and such a process cannot account for strong chemical heterogeneities inferred in the lowermost mantle and the topmost outer core, nor for ultralow-velocity zone (ULVZ)-like structures in seismically fast regions. Water-rich Bdg and PPv may be present in the large low shear velocity provinces and ULVZs, which may be the residue of a basal magma ocean and are predicted to host a deep low D/H water reservoir inherited from the early Earth that is occasionally sampled by plumes of a lowermost-mantle origin.
Read the full abstract ▾
All authors Megumi Semba, Naoya Sakamoto, Shuhei Mita, Kei Hirose, Yutaro Tsutsumi, Keisuke Ozawa, John W. Hernlund, Shiro Miwa
Plasma Physics
LoKI-GM: a global model framework for plasma chemistry studies
L. L. Alves, A. Tejero-Del-Caz, L. Marques et al. (+6 more)
Global (zero-dimensional or spatially averaged) models are widely employed to study complex chemistries in low-temperature
plasmas (LTPs). By adopting a spatially average description of the
plasma, they substantially reduce the computational cost while still providing reliable and detailed insight into the key processes taking place in the
plasma. In their most general formulation, global models involve the coupled solution of a Boltzmann solver (to describe the electron kinetics) and a Chemistry solver (to describe the heavy-species kinetics). This paper presents a tutorial on the LisbOn Kinetics Global Model (LoKI-GM) framework, developed in MATLAB and available as open-source code. The framework couples the Boltzmann solver LoKI-B, which solves the space-independent form of the two-term electron Boltzmann equation for non-magnetised non-
equilibrium LTPs, excited by DC/HF electric fields or time-dependent (non-oscillatory) electric fields, and the Chemistry solver LoKI-C, which solves the system of zero-dimensional rate balance equations for the main charged and neutral species in the
plasma and at the surface, receiving as input the kinetic schemes for the gas/
plasma/surface system under study. The inclusion of several transport models together with support for surface kinetics models are distinguishing features of LoKI-GM compared with other global chemistry models. We briefly present the formulation of LoKI-GM, including its numerical solution strategy, input/output parameters, and calculation workflow for both active discharges and afterglow
plasmas. The main differences with respect to existing global models are highlighted, and the flexibility of the code for
plasma chemistry studies is demonstrated through representative simulation results obtained across a range of gas discharge configurations and operating conditions.
Read the full abstract ▾
All authors L. L. Alves, A. Tejero-Del-Caz, L. Marques, P. Pereira, N. Pinhão, C. D. Pintassilgo, T. Silva, P. Viegas, V. Guerra
Physics and Society
Evolutionary dynamics of collective decision-making with local social influence on static and dynamic networks
Yuyuan Liu and Xiaojie Chen
Collective decision-making is ubiquitous across the living world and artificial societies. Individuals often choose an option based on intrinsic values of options. However, individual decision-making is also swayed by neighbors' choices, generating local social influence. Hence, an important question arises naturally, yet remains unanswered: when such social influence is integrated into the individual evaluation process for option choices, how does it affect collective decision-making outcomes in structured populations modeled by graphs. To address this, we consider a baseline model of binary options with social influence and assume that individuals not only evaluate the intrinsic values of options, but are also influenced by their neighbors' choices. We propose a perceived utility function integrating these two aspects for individual decision-making. By means of theoretical analysis, we first derive the average frequency of an option on static weighted connected graphs and present the mathematical condition under which this option prevails in the population. We find that the introduction of social influence can amplify the advantage of a superior option or compensate for the deficiency of an inferior one. We also reveal that the average degree of network exerts a dual effect on collective decision outcomes. Furthermore, we consider our evolutionary model on dynamic networks switching among distinct graph configurations. Our theoretical analysis shows that the evolutionary outcomes depend not only on the average degree of each network configuration, but also on its expected duration. We perform computer simulations to verify our theoretical predictions on static and dynamic networks.
Read the full abstract ▾
Computational Physics · Cross-listed from cond-mat.mtrl-sci
Effect of Al-Zn alloy wafer grain boundary diffusion on the magnetism and microstructure of sintered NdFeB magnets
Xi Liu, Wenxi Fang and Ken Perlin
This study investigates Al-Zn grain boundary
diffusion (GBD) treatment on sintered Nd-Fe-B magnets using $Al_{80}Zn_{20}$
alloy sheets as the
diffusion source. The
alloy sheets were placed at both ends of cylindrical samples and
diffusion-annealed at 900$^\circ$C and 700$^\circ$C for 7 hours under
vacuum ($\leq5\times10^{-3}$ Pa), followed by tempering at 500$^\circ$C for 2 hours.
Magnetic measurements show that coercivity increases from 951.5kA/m in the untreated sample to 1158.2kA/m at 900$^\circ$C (a gain of 206.7kA/m, 21.7%) and to 1039.6kA/m at 700$^\circ$C (a gain of 88.1kA/m, 9.3%), while remanence declines modestly from 1282mT to 1256mT after the high-temperature treatment. Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDS), and X-ray diffractometer (XRD) analyses reveal that the 900$^\circ$C treatment produces a thinner, more continuous grain boundary phase and a distinct core-shell structure around the main-phase grains. EDS mapping shows that Al preferentially enriches the shell region of the $Nd_2Fe_{14}B$ grains, while Zn predominantly resides in the grain boundary phase, where it lowers the melting point of the intergranular phase and improves its fluidity. XRD shows no detectable secondary phases, while the combined XRD, EDS results, and
lattice expansion are consistent with possible limited Al incorporation into the main-phase
lattice. Verified by computational analysis, the coercivity enhancement is attributed to three synergistic factors: improved grain boundary decoupling, the formation of a high-anisotropy shell layer that strengthens domain-wall pinning, and the smoothing of grain edges to suppress reverse-domain nucleation.
Read the full abstract ▾
Accelerator Physics
Experimental Demonstration of a Two-Dimensional Nonlinear Integrable System in a Particle Accelerator
John Wieland, Alexander Valishev, Aleksandr Romanov et al. (+4 more)
A two-dimensional nonlinear integrable system was experimentally demonstrated at the Fermilab Integrable Optics Test Accelerator. The system was implemented by inserting a special nonlinear magnet in a conventional accelerator
lattice. We characterized the system by measuring lifetimes, transverse profiles and transverse oscillation frequencies of the 150-MeV electron beam as a function of the strength of the nonlinear insert. The measured shift of the working point and the amplitude-dependent detuning were consistent with theoretical predictions. We also observed the predicted bifurcation of the stable closed orbit. A striking consequence of the system's implementation was the possibility to operate the storage ring with integer tunes without lifetime degradation. This research opens up novel ways to design particle accelerators and to stabilize particle beams.
Read the full abstract ▾
All authors John Wieland, Alexander Valishev, Aleksandr Romanov, Nikita Kuklev, Giulio Stancari, Sergei Nagaitsev, Sebastian Szustkowski
Geophysics
Anomalous-diffusion synthesis of non-Gaussian reservoir anomalies for time-lapse seismic inversion
Anderson Mateus de Sousa Nogueira, Paulo Vitor Ferreira, Katerine Rincon Perez et al. (+5 more)
We develop a physics-informed framework for learned time-lapse (4D) seismic inversion that estimates production-induced velocity changes associated with subsurface fluid migration. Existing learned inversion methods are commonly trained on seismic data generated from Gaussian
diffusion models, which fail to capture the anomalous transport characteristic of heterogeneous subsurface reservoirs. To overcome this limitation, we introduce a data generator based on space-time fractional
diffusion, in which the temporal and spatial fractional orders independently control
memory effects and nonlocal transport, while elliptical anisotropy represents preferential flow. By sampling this parameter space, we generate a broad ensemble of physically consistent velocity perturbations spanning normal, subdiffusive, superdiffusive, and intermediate transport regimes. We then train a convolutional neural network to map time-lapse seismic residuals directly to velocity updates. Through extensive Monte Carlo validation, we show that the network accurately reconstructs production-induced anomalies across all transport regimes, with reconstruction errors governed primarily by anomaly amplitude and interface sharpness rather than by the
diffusion regime itself. Our results demonstrate that
embedding anomalous-transport physics into the training distribution substantially extends the applicability of amortized 4D seismic inversion, enabling robust recovery of heavy-tailed and anisotropic reservoir signatures beyond the Gaussian assumptions underlying existing approaches.
Read the full abstract ▾
All authors Anderson Mateus de Sousa Nogueira, Paulo Vitor Ferreira, Katerine Rincon Perez, João M. de Araújo, Tiago Barros, Samuel Xavier-de-Souza, Sérgio Luiz da Silva, Gilberto Corso
Accelerator Physics
Energy-resolved measurement of individual GeV muon tracks generated by electrons from a compact Laser-Plasma Accelerator
Davide Terzani, Luc Le Pottier, Stanimir Kisyov et al. (+17 more)
Recently, the possibility of LPA-produced
muon beams has gained significant interest within the accelerator application community. Directional, multi-GeV
muons can be produced via Bethe-Heitler interactions when multi-GeV electrons hit solid targets. They are highly penetrating and, thanks to the compactness of the LPA, offer a path toward a deployable, active
muon source. At the BELLA Center of the Lawrence Berkeley National Laboratory, we previously unambiguously detected
muons generated during the interaction of multi-GeV electron beams with a 4 meter-thick electron beam dump. A new campaign has now extended our diagnostic capabilities to single-
muon trajectory reconstruction and energy measurements. The setup allowed us to individually reconstruct each
muon trajectory, defined by us as a
muon passing through three detectors used for the reconstruction. For a subset of events, we extracted the
muon energy from the
magnetic-field bending angle, demonstrating production of GeV-scale
muons. This work provides a key demonstration of track-based active-source muography, which enables non-invasive 3D density mapping of concealed or inaccessible samples, and it will accelerate the development of active LPA-based
muon sources where compactness, controlled directionality, low divergence, and deep penetration are required.
Read the full abstract ▾
All authors Davide Terzani, Luc Le Pottier, Stanimir Kisyov, Pranav Manoj, Ryan Heller, Maria Mironova, Alex Picksley, Joshua Stackhouse, Hai-En Tsai, Raymond Li, Timon Heim, Maurice Garcia-Sciveres, Carlo Benedetti, John Valentine, Kei Nakamura, Anthony J. Gonsalves, Jeroen van Tilborg, Carl B. Schroeder, Eric Esarey, Cameron G. R. Geddes
Computational Physics
Learning Lattice Parameters from Powder X-Ray Diffraction Data Using Invariants
Elyssa Hofgard, Kyucheol Min, Nofit Segal et al. (+8 more)
We present a machine learning (ML) method to determine unit
cell parameters from powder X-Ray diffraction (XRD) data using a novel invariant
lattice representation. In ML, the data representation used can have a substantial impact on the prediction quality. Previous approaches have directly predicted
lattice parameters ($a,b,c,\alpha,\beta,\gamma$) from XRD inputs. However, these parameters depend strongly on the unit
cell reduction or convention used. In this work, we construct an invariant representation of the reciprocal
lattice that is independent of primitive
cell convention, based on the bispectrum–a descriptor built from spherical harmonic projections of
lattice points. The calculation of the
lattice bispectrum is differentiable, and we demonstrate how to invert it using gradient-based optimization initialized from a nearest-neighbor lookup. We show that with a fixed ML model architecture, using the
lattice bispectrum as the ML target rather than the unit
cell parameters leads to more accurate
lattice parameter predictions. For example, using the MP-20
dataset, the bispectrum reduces length mean absolute percentage error (MAPE) from 11.08% to 2.43% and angle MAPE from 12.15% to 2.45% compared to direct prediction with the same model architecture. We additionally
benchmark our approach against pre-existing XRD to
crystal structure models such as Crystalyze and assess its performance on experimental data. Beyond unit
cell representation, we anticipate this invariant
lattice representation could serve more broadly as a geometry-aware target for other crystallographic machine learning tasks such as structure generation.
Read the full abstract ▾
All authors Elyssa Hofgard, Kyucheol Min, Nofit Segal, David W. Mittan-Moreau, Aria Mansouri Tehrani, Vanessa Oklejas, Rafael Gómez-Bombarelli, Jigyasa Nigam, Daniel W. Paley, Aaron S. Brewster, Tess Smidt
Atomic Physics · Cross-listed from astro-ph.GA
Emissivity line ratios for [Mn III] and spectral diagnostics of H II regions
Zher Samak, Sultana N. Nahar and Anil K. Pradhan
We present the first theoretical emission-line study of Mn III as potential determinant of physical conditions and manganese abundance. We compute atomic data for a set of Mn III lines and line emissivity ratios as temperature-density diagnostics. Accurate relativistic Breit-Pauli R-
matrix calculations have been carried out for electron impact excitation of Mn III transitions that have not been previously studied. Selected forbidden lines are shown to be sensitive to temperature and density under nebular conditions in H II regions such as SNRs. The coupled channel R-
matrix calculations include a wavefunction expansion that includes 38 levels of Mn III dominated by the ground and first excited electronic configurations $3d^5$ and $3d^44s$. Collision strengths for all 703 forbidden transitions among those levels, and Maxwellian averaged rate coefficients are obtained. A collisional-radiative model yields emissivity line ratios using calculated collision strengths and radiative decay A-values. Based on the present analysis, certain [Mn III] lines are predicted to be sensitive to density and/or in the typical nebular range. The detection of those lines could also yield
cosmic Mn abundance relative to other elements.
Read the full abstract ▾
Biological Physics · Cross-listed from cond-mat.soft
Quantifying reticulocyte biomechanics in health and disease
Zhaojie Chai, Jianlu Zheng, He Li et al. (+2 more)
Red blood
cell (RBC) populations are mechanically and morphologically heterogeneous, yet how this heterogeneity governs transport, splenic retention and blood rheology in confinement remains unclear. We combine microchannel experiments with dissipative particle dynamics (DPD) simulations to determine how the morphology, deformability and hydrodynamic interaction of immature RBCs (reticulocytes) shape microconfined flow in acute and chronic mountain sickness. Reticulocyte-rich samples present the three shapes that the maturation literature assigns to successive reticulocyte stages – multilobular, cup-shaped and near-discocytic – which we model as R1-R3, each with a membrane shear modulus within the range reported for reticulocytes. A 5-um microchannel resolves these models only weakly, R1 taking at most ~18% longer than control discocytes to cross it, whereas a 1.5-um splenic slit, driven at its own loading, delays R1 by ~30%; both geometries order the models by shear modulus. In
cell pairs, a leading
cell never lets a follower pass below its own single-
cell threshold, ruling out the order-of-magnitude reduction that a wake-"unjamming" picture would suggest; instead the follower queues behind the leader, and a stiffer leader, which clears the slit more slowly, delays it more. The controlling variable is the single-
cell critical pressure gradient Delta P_c, which rises monotonically from control discocytes through the reticulocyte subtypes to sickled
cells. Set against published rheograms, an analytical estimate attributes chronic-mountain-sickness hyperviscosity mainly to hematocrit-driven crowding rather than single-
cell rheology. These results place benign acclimatization, chronic-mountain-sickness hyperviscosity and sickle-
cell-trait splenic syndrome on a single mechanical axis defined by Delta P_c.
Read the full abstract ▾
All authors Zhaojie Chai, Jianlu Zheng, He Li, Ming Dao, George Em Karniadakis
Medical Physics
A Dual Path Framework with Hotspot Guided Fusion for Three Dimensional CT to PET Synthesis in Head and Neck Cancer
Mohd Maaz Khan and Oluwaseyi Oderinde
18F-FDG PET/CT plays a central role in staging, treatment planning, and response assessment for head and neck cancer by providing functional information that complements anatomical CT imaging. However, PET acquisition requires radiotracer administration, specialized infrastructure, and additional cost, limiting its availability for repeated imaging. We present a proof of concept deep learning framework for synthesizing PET like images directly from routine CT scans with the goal of providing complementary metabolic information that may support imaging triage and clinical decision support rather than replace diagnostic PET. Forty-four patients from the publicly available QIN-HEADNECK
dataset were retrospectively analyzed using five fold cross-validation. We propose a fully three dimensional dual path architecture consisting of (i) a regression U-Net optimized for voxel-wise quantitative SUV estimation and (ii) a conditional generative
adversarial network optimized for realistic PET texture. Their outputs are integrated using hotspot guided
Laplacian pyramid blending, allowing quantitative information from the regression pathway to be preserved within metabolically active regions while leveraging
adversarial texture synthesis elsewhere. The proposed framework achieved a mean absolute error of 0.00395, PSNR of 39.19 dB, and SSIM of 0.9634 on reconstructed three dimensional PET volumes. Qualitative evaluation demonstrated accurate localization of many FDG-avid lesions while producing anatomically realistic background texture. Consistent with previous CT to PET synthesis studies, the principal limitation was systematic underestimation of SUV within highly metabolically active tumor regions.
Read the full abstract ▾
Fluid Dynamics
Load-dependent Taylor dispersion in a compliant electroosmotic pump conveying a simplified Phan-Thien-Tanner fluid
Subhajyoti Sahoo and Ameeya Kumar Nayak
We develop a coupled model for electroosmotic pumping and passive-solute dispersion of a solvent-free simplified Phan-Thien-Tanner fluid in a compliant slit microchannel. Pressure, wall deformation, axial field, velocity, and dispersion are evaluated self-consistently along the finite-throughput pump characteristic. Lubrication theory, Debye-Huckel electrostatics, an elastic-foundation wall law, and Taylor-Aris macrotransport yield a closed-form flux relation for combined electroosmotic and pressure-driven forcing. Because the shear rate depends cubically on the total shear stress, the two contributions cannot be superposed. The flux decreases monotonically with pressure gradient, ensuring a unique inversion at prescribed throughput. Current conservation couples the axial field to the deformed gap under constant-current and constant-voltage operation. In pressure-free flow, thinning the electric double layer produces a plug-like profile and the Newtonian Taylor coefficient decays as the inverse square of the Debye parameter. Under hydraulic loading, an adverse pressure gradient drives a sheared core counterflow that persists in the thin-double-layer limit, causing the coefficient to approach a finite plateau. At fixed nonzero throughput, partial cancellation between electroosmotic and pressure-driven shear yields a maximum plate number at finite double-layer thickness. This optimum is conditional: joint optimization over throughput and double-layer thickness shifts the overall optimum toward free-flow, thin-double-layer operation. Viscoelasticity can enhance or suppress loaded dispersion, while compliance shifts the pump characteristic and separation optimum. Brownian dynamics validates the reduced model. The resulting load-resolution relation identifies conditions that balance pressure delivery and separation performance.
Read the full abstract ▾
Chemical Physics
Graph-Theoretic Neural Network Fragmentation with Covariant Direct Molecular Force Learning: Enabling Coupled-Cluster Accuracy AIMD for Fluxional Systems
Xiao Zhu and Srinivasan S. Iyengar
Accurate ab initio molecular dynamics (AIMD) simulations of complex, fluxional chemical systems are severely limited by the high computational scaling of correlated electronic structure methods. To overcome this bottleneck, we present a robust, graph-theoretic molecular fragmentation framework integrated with machine learning to directly model post-Hartree-Fock
nuclear forces at coupled cluster accuracy. Bypassing the limitations of automatic differentiation on learned energy surfaces that may struggle with link-atom Jacobians, our approach directly predicts
nuclear force vectors. By projecting these vectors onto fragment-fixed principal axes of inertia, we establish co-variant descriptors that naturally preserve rotational, translational, and permutational invariance. The methodology achieves exceptional high parameter efficiency through a vector-valued training protocol that reduces trainable parameters by over an order of magnitude, while an unsupervised mini-batch k-means space tessellation
algorithm constructs highly representative training databases using only 10% to 20% of reference configurations. We rigorously validated this framework on the highly fluxional solvated Zundel cation H_{13}O_6^+ ). Our fully machine-learning-predicted AIMD trajectories successfully reproduced complex dynamical signatures and key structural characteristics, including radial distribution functions and the velocity autocorrelation power spectrum. Ultimately, this scalable, systematically improvable framework bridges the gap between high-level correlated wavefunction theories and long-timescale reactive sampling, laying the foundation for advanced, LLM-inspired transfer learning in modern chemical dynamics simulations.
Read the full abstract ▾
Optics
Time diffraction of optical helicity
Alex J. Vernon, Jingyi Wu, Anton Y. Bykov et al. (+4 more)
If in a classic double-slit interference experiment the light that passes though one slit is in an orthogonal polarisation state to that of the second slit, no visible interference fringes emerge. Interference fringes are instead present in a different observable that relates to the difference in energy carried by two orthogonal polarisation components, causing spatially varying polarisation patterns: the optical helicity density in the case of linearly polarised fields. Here, we develop a generalised treatment of interference in space and time, and experimentally demonstrate the helicity patterns produced by interference of orthogonally polarised pulses, which would be produced by two temporal slits in time diffraction observations. The developed approach may be important for understanding and applications of complex polarisation patterns and polarisation effects in time varying media.
Read the full abstract ▾
All authors Alex J. Vernon, Jingyi Wu, Anton Y. Bykov, Guy L. Whitworth, Henry Cossey, Francisco J. Rodríguez-Fortuño, Anatoly V. Zayats
Optics
Reliability-Aware Bayesian Optimization of 1310 nm PCSELs with FDTD Verification
Jinglin Yu, Feiyang Wu, Longying Wen et al. (+3 more)
Near 1310 nm photonic-
crystal surface-emitting
lasers (PCSELs) are attractive narrow-beam sources for optical communication and sensing, but their final design refinement is costly. Small geometry changes simultaneously shift the band-edge resonance, cavity leakage, far-field divergence, and the numerical stability of a high-$Q$ decay fit, while every full-wave trial requires a time-domain simulation. We couple a commercial finite-difference time-domain solver to a reliability-aware
Bayesian optimization (BO) loop over eight local design variables. Each completed simulation updates the surrogate used to choose the next geometry. Candidate ranking combines wavelength and beam-quality requirements with a reliability-adjusted metric $Q_{\mathrm{eff}}$ derived from the solver-reported relative fit-error estimate $dQ/Q$. Across three 80-evaluation runs from the same reference model, BO produced 5–15 candidates per run that passed the joint filter. Designs reconstructed from fresh model copies retained $Q_{\mathrm{eff}}=4.33\times10^6$–$7.76\times10^6$, a 60–108-fold increase over the baseline metric, at 1308.23–1310.90~nm with approximately $0.84^{\circ}$ divergence. Under equal budgets, BO gave the highest mean strict-filter yield (9.0 candidates), compared with differential
evolution (7.0) and Latin-hypercube sampling (1.5), although the controls occasionally matched the peak $Q_{\mathrm{eff}}$. Field maps, resonance spectra, and local perturbations further identify an index-related wavelength handle and a hole-size-related leakage handle. The resulting FDTD budget produces a pool of wavelength-compatible, narrow-beam, and reproducible high-$Q$ PCSEL candidates without trusting a single optimistic decay fit.
Read the full abstract ▾
All authors Jinglin Yu, Feiyang Wu, Longying Wen, Chongxian Yuan, Renjie Li, Zhaoyu Zhang
Plasma Physics · Cross-listed from math-ph
Nonlinear Schrödinger equation on a closed 3D elastica knot
Alain J. Brizard
The present work introduces a new relation between closed elastica
knots with the solution of the nonlinear Schrödinger equation (NLSE) through the Hasimoto transformation. An elastica
knot is defined in terms of the Frenet-Serret
curvature $\kappa(s,t)$ as a function of the arclength $s$ along the spatial curve ${\bf r}(s,t)$ at a fixed time $t$, which is a solution of the
curvature differential equation $\partial^{2}_{s}\kappa(s,t) = -\;\kappa^{3}/2 + k_{0}^{4}\tau_{0}^{2}\;\kappa^{-3} + \lambda\,k_{0}^{2}\kappa/2$. Here, the Frenet-Serret torsion $\tau(s,t)$ satisfies the conservation law $\kappa^{2}(s,t)\,\tau(s,t) \equiv k_{0}^{2}\,\tau_{0}$, while the constant of integration $\lambda$ is associated with the constrained variation. After briefly reviewing the Hasimoto transformation from a space curve ${\bf r}(s,t)$ to the nonlinear Schrödinger equation (NLSE) $-\,iD^{-1}\partial_{t}\psi = \partial^{2}_{s}\psi + \frac{1}{2}\,|\psi|^{2}\psi$, where the constant $D$ has units of fluid circulation (m$^{2}$/sec), we show how the traveling-wave solution $\psi(s,t) = \Psi(s_{t} \equiv s - c\,t) \equiv \kappa(s_{t})\;\exp[i\theta(s_{t})]$ is mapped onto the
curvature equation for an elastica
knot, with $\theta^{\prime}(s_{t}) \equiv c/(2D) + k_{0}^{2}\tau_{0}/\kappa^{2}(s_{t})$ and the elastica-
knot constant $k_{0}^{2}\lambda = -\frac{1}{2}\,(c/D)^{2}$ expressed in terms of the traveling-wave NLSE parameters $(c,D)$. The constraint of a closed 3D elastica
knot imposes spatial periodicity conditions that introduce a unique set of
knot parameters for which the NLSE traveling wave can exist. The present work shows that the NLSE traveling-wave solution on a closed elastica
knot requires an extension of the classical elastica-
knot parameter space.
Read the full abstract ▾
Optics
Towards on-chip nascent all-van-der-Waals polarization optical components for nanoscale photonic applications
Dmitrii Litvinov, Ilia Begichev, Iakov Reznikov et al. (+8 more)
The integration of polarization-control elements into nanoscale photonic
circuits remains a central challenge for modern on-chip optical technologies, which call for continuous miniaturization. Van der Waals (vdW)
crystals provide a versatile platform for the creation of such components owing to their strong optical anisotropy, high-refractive indices and atomically precise
heterostructure assembly capabilities. In this work, we demonstrate an approach towards the creation of all-vdW on-chip polarization optical components, exemplified with quarter-wave plates operating in the near-infrared (NIR) spectral region, realized in specifically twisted ReSe2/alpha-MoO3 vdW
heterostructures on a Si/SiO2 platform. Here, low-
symmetry ReSe2 layer serves as a source of exceptionally high linearly polarized excitonic emission, whereas in-plane birefringent alpha-MoO_3 provides polarization-state conversion. Furthermore, our finite-difference time-domain (FDTD) simulations quantitatively reproduce the experimental observations with high accuracy revealing the critical roles of layer thicknesses, twist-angle, Fabry-Perot interference and emitter distribution effects in the determination of polarization conversion efficiency, which yields up to 95 % degrees of circular polarization (DoCP) for the optimized parametrization. Our findings establish a practical route towards fully integrated all-vdW polarization optical components, providing a foundation for nanoscale photonic architectures based entirely on layered materials.
Read the full abstract ▾
All authors Dmitrii Litvinov, Ilia Begichev, Iakov Reznikov, Changyi Chen, Maksim Sargsyan, Sergey Y. Grebenchuk, Makars Siskins, Kostya S. Novoselov, Alexey I. Berdyugin, Maciej Koperski, Davit A. Ghazaryan
Geophysics · Cross-listed from astro-ph.EP
Onset of dynamo action in planetesimals
Ludovic Huguet, Jonathan E. Mound, Christopher J. Davies et al. (+1 more)
Several meteorites have been found to carry primary remanent magnetizations imparted by fields generated within planetesimal cores during the early
solar system. Thermal
evolution models have shown that thermal convection likely drove the dynamo in the early
evolution of these bodies. In such small cores, the
magnetic Reynolds number is thought to be close to the threshold for dynamo action. However, the critical value of the
magnetic Reynolds number, meaning its value at the onset, is also poorly constrained in dynamo simulations. We perform dynamo simulations to investigate the onset of the dynamo at different Ekman ($E$) and
magnetic Prandtl ($Pm$) numbers, in a quasi-full sphere. Along two empirical paths in this $(E,Pm)$ space, the onset of dynamo action depends on whether the
magnetic field is initially strong or weak. The onset of the dynamo occurs at larger supercriticality (ratio between the Rayleigh number ($Ra$) and its critical value ($Ra_c$)) when moving toward more realistic parameter values. Once extrapolated to planetesimal core conditions, the supercriticality for the onset of the dynamo is about $10^3$ for a strong initial
magnetic field (meaning
magnetic energy is of the same order of magnitude or larger than the kinetic energy). For a weak initial field, the required $Ra/Ra_c$ would be larger. Compared to previous estimates, this revised criterion facilitates dynamo activity, and so extends the lifetime of the
magnetic field compared to previous models and allows the generation of a
magnetic field in smaller planetesimals.
Read the full abstract ▾
All authors Ludovic Huguet, Jonathan E. Mound, Christopher J. Davies, James F.J. Bryson
Optics · Cross-listed from quant-ph
Deleterious effect of photon-phonon coupling on microcavities in their application as quantum sources
Y. Sacha C. L. S., G. C. Rickli, J. Dipold et al. (+4 more)
In
quantum systems, the contact with the environment is detrimental to the purity of the state, thus limiting the practical use of entangled sources in
quantum information applications. This loss of purity is observed in the form of additional noise in the
tomography of the state. We investigate this noise dependence in $Si_3N_4$ micro-cavities, previously used for
quantum state generation, and demonstrate that the dependence of this noise on the temperature is compatible with a coupling of the photonic chips to a thermal reservoir. The control of this noise source is a necessary condition for the efficient implementation of these devices as sources of entangled states in
quantum networks.
Read the full abstract ▾
All authors Y. Sacha C. L. S., G. C. Rickli, J. Dipold, R. A. Kögler, Paulo Nussenzveig, Nathália B. Tomazio, M. Martinelli
Medical Physics · Cross-listed from cs.ET
Quantum Adaptive Sensing for Accelerated MRI
Asmit Ganguly, Suprajit Dewanji, Chenyang Zhao et al. (+1 more)
Compressed sensing accelerates MRI by reconstructing images from undersampled k-space, but performance depends strongly on sampling distribution. We propose an adaptive framework that selects Cartesian phase-encode lines sequentially using a fixed-cardinality quadratic unconstrained binary optimization (QUBO) formulation. The objective combines a preference for central k-space, signal-energy information from previously acquired measurements, and pairwise terms that encourage spatially dispersed sampling. The formulation is compatible with classical annealing and
quantum-annealing hardware. Retrospective experiments used simulated eight-coil 3D MRI data; QUBO problems were solved with parallel tempering, and images were reconstructed with SENSE and total-variation regularization. At 20% and 10% sampling, the proposed method improved PSNR, SSIM, NMSE, and HFEN compared with the evaluated static Cartesian strategies, including variable-density Poisson-disc sampling, although gains varied with resolution, acceleration, and noise level. In a reduced-pool experiment, a D-Wave
quantum-classical hybrid solver achieved reconstruction quality comparable to variable-density Poisson-disc sampling, demonstrating feasibility on current
quantum optimization infrastructure. While these results do not establish
quantum computational advantage, the direct QUBO representation provides a practical framework for adaptive MRI sampling and may benefit from future advances in
quantum-annealing hardware. Prospective scanner validation and systematic
quantum-classical benchmarking remain necessary.
Read the full abstract ▾
All authors Asmit Ganguly, Suprajit Dewanji, Chenyang Zhao, Danny J. J. Wang
Computational Physics
On the Removal of Solver-Induced Dependencies in Momentum-Weighted Interpolation for Primal and Continuous-Adjoint Flow Solvers
Niklas Kühl
Momentum-Weighted Interpolation (MWI) is a key component in pressure–velocity coupling schemes on collocated
cell-centered finite-volume methods for both primal and continuous adjoint formulations. In many practical implementations, MWI relies on diagonal momentum coefficients that include contributions from under-relaxation and time discretization. As a result, both primal quantities of interest and adjoint sensitivities may exhibit a non-physical dependence on solver parameters such as relaxation factors and time-step size, and no well-defined limit is obtained as these parameters approach zero. In this work, building on previous developments in discrete-consistent MWI formulations, a simple correction is proposed that removes solver-induced contributions from the diagonal momentum coefficients in the pressure-driven term. The resulting formulation preserves the original discretization while eliminating artificial dependencies on relaxation and time-stepping parameters and is applied consistently to both primal and adjoint systems. To facilitate its application, the derivation is presented in a structured, recipe-like manner that can be readily followed and transferred to different finite volume-based solver configurations. The proposed modification is assessed for a two-dimensional laminar cylinder flow and a three-dimensional turbulent ship hull flow configuration. In both cases, the uncorrected formulation leads to significant variations in forces, wake-related quantities, and shape sensitivities when solver parameters are altered, despite all simulations being iterated to converged residual levels and stable integral quantities. In contrast, the corrected formulation yields consistent results across a wide range of relaxation factors and time-step sizes.
Read the full abstract ▾
Optics
How to calculate the Wigner angle
C. J. McKinstrie and M. V. Kozlov
Lorentz transformations in time and two space dimensions consist of boosts and rotations, and combinations thereof. In general, the combination of two boosts is not another boost: It is a boost followed by a rotation. The rotation angle is called the Wigner angle. Although it is straightforward to determine the energy and direction of the combined boost, it is difficult to determine the Wigner angle. In this article, the vector,
matrix and spinor derivations of formulas for the Wigner angle are reviewed, and the underlying mathematics and physics are discussed briefly. Although the derivations are different, the results they produce are equivalent, as they should be. Like many physics problems, if one looks at the problem in the right way, it is not difficult to solve.
Read the full abstract ▾
Plasma Physics
A Multi-Species Reactive-Boltzmann Formulation for Self-Consistent Kinetic Simulation of Burning Fusion Plasmas
Mark Dunn, Jingwei Hu and Uri Shumlak
Discrepancies between experimental data and radiation-hydrodynamic models of burning
plasmas at the National Ignition Facility have been attributed, in part, to possible deviations of reactant ion distributions from Maxwellian
equilibrium. In particular, it has been hypothesized that the collisional relaxation of energetic fusion products with the bulk
plasma may generate suprathermal ion populations not captured by reduced models. To assess this hypothesis in a fully kinetic setting, we present a multi-species reactive–elastic kinetic framework, in which fusion sources and sinks are evaluated directly from the reactant velocity distribution function with a reactive Boltzmann collision operator. For computational efficiency, elastic interactions are modeled in the small-angle collision limit using the Landau and Lenard–Bernstein collision operators, although the framework admits large-angle elastic scattering generalizations. The integro-differential collision operators are discretized with a fast
Fourier spectral method, enabling efficient, high-order accuracy evaluation of reactive processes in three-dimensional velocity space and providing a deterministic alternative to Monte Carlo collision methods. Numerical experiments are performed for spatially homogeneous two- and three-species D–D fusion systems in weakly coupled, early-time regimes. We find that fusion product heating does not generate a significant suprathermal population in the reactant ions: deviation from the corresponding Maxwellian distribution remains small in both the Frobenius norm and the fusion reactivity.
Read the full abstract ▾
History and Philosophy of Physics
Dimensional Analysis is a Gauge Theory
Benjamin Muntz
I argue that dimensional analysis can appropriately be thought of as a gauge theory. This picture naturally leads to the usual quantity calculus through inherent properties of Lie groups, Lie
algebras, and representation theory. The gauge theory interpretation is perhaps strongest for non-constant units. I explain how Stevens's classification of scales of measurement can be understood by choices of different gauge groups. Finally, I reinterpret and rephrase the Buckingham-{\Pi}
Theorem in a way that also applies to typical gauge theories. Counting the number of ”{\Pi}”s becomes a well-known problem of invariant theory.
Read the full abstract ▾
Optics
Micro-electromechanical photonic integrated memristors
Matthew Zimmermann, Julia M. Boyle, Hardit Singh et al. (+7 more)
Programmable optical memristors embedded in photonic integrated
circuits (PICs) are emerging as an important technology for high-speed optical storage and in-
memory optical computing applications. These devices provide multi-level, non-volatile storage of optical phases that can be interrogated at the speed of light, enabling parallel data readout or energy-efficient multiply-accumulate operations in artificial neural networks. However, there remains several outstanding challenges with existing optical memristor technology including durability, material-induced optical losses, large-scale reconfigurability, or fabrication yield for realistic applications. Here we introduce an analog-programmable photonic memristor based on photonic integrated micro-electromechanical (MEMS) cantilevers produced in a CMOS foundry. The memristor consists of low-loss silicon nitride waveguides, requires no additional back-end materials integration, and is all electrically programmed with electrostatic-piezoelectric forces. We demonstrate up to 5-bit phase storage levels, 50 kbit/s programming speeds, strain-assisted non-
volatility lifetimes >1 hour, >1 billion cycle endurance, and stress-tested millions of write-read cycles with pseudorandom bit sequences. We further extend the
memory lifetime to several days with simple electronic refresh
circuits in a portable battery-powered module, demonstrating a proof-of-concept optical random-access
memory in static or dynamic configurations. Our MEMS-photonics technology represents an important step toward practical optical memristors.
Read the full abstract ▾
All authors Matthew Zimmermann, Julia M. Boyle, Hardit Singh, Alex Witte, Kevin Palm, Thuy-Linh Le, Andrew J. Leenheer, Daniel Dominguez, Matt Eichenfield, Mark Dong